Phased chain assemblies

ABSTRACT

A chain and sprocket system includes a plurality of chains and phased or offset sprockets. The transmission system includes a random or hybrid chain with the offset sprockets. The timing system can include single or dual overhead camshafts, with phasing of the crankshaft sprockets and camshaft sprockets.

This application is a continuation in part of U.S. application Ser. No.07/885,194, filed May 19, 1992, now abandoned entitled "Phased ChainAssemblies."

This application relates to the subject matter of U.S. application Ser.No. 08/131,977, filed Oct. 4, 1993, entitled "System Phasing of OverheadCam Engine Timing Chains."

BACKGROUND OF THE INVENTION

The present invention relates generally to power transmission chains.The invention has particular application to power transmission chains ofthe inverted tooth or silent chain variety, which are used in enginetiming applications as well as in the transfer of power from a torqueconverter to a transmission or in a transfer case of a four-wheel drivevehicle.

The invention relates to phasing of the chain assemblies and thesprockets to modify the impact noise spectrum and chordal action noisespectrum. Specifically, the invention includes the use of timing chainsin conjunction with phased sprockets to alter the noise spectra in anengine timing system. The invention also includes the use of randomchains in conjunction with phased sprockets to alter the noise spectra.

Power transmission chains are widely used in the automotive industry.Such chains are used for engine timing drives as well as for thetransfer of power from the torque converter to the transmission or forthe transfer of power in a transfer case. Power transmission chains arealso widely used in industrial applications.

One type of power transmission chain is referred to as "silent chain".Such chain is formed of interleaved sets of inverted tooth links. A setor rank of links is assembled from several links positioned alongside ofor adjacent to each other. The links are connected by pivot means, whichare typically round pins received in a pair of apertures. An example ofsilent chain is found in U.S. Pat. No. 4,342,560, which is incorporatedherein by reference.

Conventional silent chains typically include both guide links andinverted tooth links. The guide links are positioned on the outsideedges of alternate sets of links. The guide links typically act toposition the chain laterally on the sprocket. Guide links typically donot mesh with the sprocket.

The inverted tooth links, or sprocket engaging links, provide thetransfer of power between the chain and sprocket. Each inverted toothlink typically includes a pair of apertures and a pair of depending toesor teeth. Each toe is defined by an inside flank and an outside flank.The inside flanks are joined at a crotch. The inverted tooth links aretypically designed so that the links contact the sprocket teeth totransfer power between the chain assembly and the sprocket. The invertedtooth links or driving links contact the sprocket teeth along theirinside link flanks or their outside link flanks or combinations of bothflanks. The contacts between the links and the sprocket teeth can be ofthe type which provide a power transfer, or can be of the nature of anincidental contact, or can include root contact or side contact.

A conventional silent chain drive is comprised of an endless silentchain wrapped about at least two sprockets supported by shafts. Rotationof a driving sprocket causes power transmission through the chain andconsequent movement of a driven sprocket. In an engine timing driveapplication, the driving sprocket is mounted on the engine crankshaftand the driven sprocket mounted on the camshaft. The rotation of acamshaft is thus controlled by and dependent on the rotation of thecrankshaft through the chain. A chain for an engine timing driveapplication is shown in U.S. Pat. No. 4,758,210, which is incorporatedherein by reference.

A conventional chain drive may include a chain assembly of extendedwidth in order to provide a chain of greater strength. Alternatively,two chain assemblies may be placed side-by-side between pairs ofsprockets in order to achieve the equivalent power transmission resultsas a single extended width chain.

Engine timing systems conventionally include at least one drivingsprocket located on the crankshaft and at least one driven sprocketlocated on the camshaft. Rotation of the crankshaft causes rotation ofthe camshaft through the chain and sprocket system.

The most basic conventional engine timing system typically includes asingle sprocket on the crankshaft connected to a single sprocket on thecamshaft, with the crankshaft sprocket having one-half the number ofteeth of the camshaft sprocket. Such a camshaft typically controls thevalve train operation through hydraulic lifters and rocker armsconnected to the valve stems. The chain can be of a narrow width inconstruction, such as shown in U.S. Pat. No. 4,758,210, which isincorporated herein by reference.

A more complicated engine timing system of the prior art connects thecrankshaft with two overhead camshafts by a pair of chains. Thecrankshaft includes two sprockets. Each chain is connected to a singlesprocket on each of the two overhead camshafts. Typically, the chainsystems will include tensioners on the slack side of each chain tomaintain chain tension and snubbers on the tight side of each chain tocontrol chain movement during operation.

More complicated engine timing systems are also utilized in the priorart. Such systems include timing systems having two (or dual) overheadcamshafts for each bank of cylinders. The dual camshafts on a singlebank can both be rotated by connection to the same chain. Alternatively,the second camshaft can be rotated by an additional camshaft-to-camshaftchain drive. The cam-to-cam drive chain can also include single or dualtensioners for chain control. All of these structures are known invarious forms in the prior art.

Conventional timing systems of the prior art can also include morecomplicated structures than a single sprocket on the crankshaft drivinga single sprocket on a camshaft. Some systems include an idler sprocketbetween the crankshaft and camshaft. One chain system drives the idlerwhich in turn drives either single or dual overhead camshafts. Thesizing of the idler gear is such as to allow different rotational speedsof the crankshaft and camshaft. For example, the crankshaft may rotatetwice the speed of the crankshaft by the sizing of the sprockets for thechain and sprocket drive system.

Noise is associated with chain drives. Noise is generated by a varietyof sources, but in silent chain drives it can be caused, in part, by theimpact sound generated by the collision of the chain and the sprocket atthe onset of meshing. The loudness of the impact sound is affected by,among other things, the impact velocity between the chain and thesprocket and the mass of chain links contacting the sprocket at aparticular moment or time increment.

The meshing impact sound is generally a periodic sound in chain drives.The impact sound is repeated with a frequency generally equal to that ofthe frequency of the chain meshing with the sprocket. The frequency isrelated to the number of teeth on the sprocket and the speed of thesprocket. The impact can produce sound having objectionable pure sonictones.

Another cause of noise in chain drives is the chordal action of thechain and sprockets as the chain is driven about the sprockets. Chordalaction occurs as the chain link enters the sprocket from the free chain.The meshing of the chain and sprocket at the chain mesh frequency cancause a movement of the free chain or span (the part of the chainbetween the sprockets) in a direction perpendicular to the chain travelbut in the same plane as the chain and sprockets. This vibratorymovement can also produce an objectionable pure sonic tone at thefrequency of the chain mesh frequency or a derivative of it.

Many efforts have been made to decrease the noise level and pitchfrequency distribution in chain drives of the silent chain variety tominimize the objectionable effects of the pure sonic tones. The problemof noise reduction in silent chain drives was addressed in U.S. Pat. No.4,342,560 by changing the contacts between the link flanks of a silentchain and the sprocket teeth by having differently configured linkflanks in different sets of the chain. By mixing links of differingflank configuration, U.S. Pat. No. 4,342,560 attempted to modify thepattern of sound emanating from the chain contacting the sprocket byaltering the types of link configurations and thus altering the pointand rhythm of contacts. A similar concept was used in U.S. Pat. No.4,832,668. Each of these patents teaches the reduction of chain noiselevel by randomization of elements within the chain, such as linkconfiguration or profile, or link aperture-to-flank spacing distance.

U.S. Pat. No. 4,915,675which is incorporated herein by reference,utilized the same concept of modifying the pattern of sound emanatingfrom the chain by altering the types of link configurations. That patentteaches the utilization of an asymmetrically shaped link form which isthen oriented in two different directions in the chain assembly to alterthe point and rhythm of chain to sprocket contacts.

Other attempts to alter the rhythm of contacts between the silent chaindrive and the sprocket have focused on the modification of elementswithin the sprocket, such as the sprocket tooth profile or the spacingof the sprocket teeth on the sprockets. For example, U.S. Pat. Nos.3,377,875 and 3,495,468, which are both incorporated herein byreference, teach modification of certain sprocket teeth or evenelimination of some teeth in order to achieve noise reduction incontacts between the links of the silent chain and the sprocket teeth.

The present invention is directed to noise reduction by modification ofthe impact sound pattern and the chordal action sound pattern, which aregenerated by chain and sprocket contacts. The invention attempts tomodify those sound patterns by various phasing relationships between thechain assembly and the sprockets. Phasing the chain and sprocketrelationship can reduce the number of chain link teeth (or mass ofchain) impacting the sprocket during a given time increment. Similarly,phasing the chain and sprocket relationship can alter or phase thechordal action or articulation of the chain and sprocket. Both of thesephasing modifications, alone and in conjunction with the randomizationof the chain and sprocket contacts, can alter the impact and chordalaction generated sound patterns.

With regard to use of phasing relationships in the prior art, a manualtransmission drive of the Saab 99 vehicle used three individual rollerchains in parallel on three separate, spaced-apart sprockets. Theseroller chains differ from the inverted tooth chains of the presentinvention and have different power transmission and noisecharacteristics. The three identical roller chains were run in parallelwith each chain and sprocket phased by 1/3 pitch relative to theadjacent chain and sprocket. This system is described in an August 1980ASME paper entitled "Roller Chain as a Transfer Drive for theAutomobile." A roller chain system with offset sprockets is also shownin U.S. Pat. No. 3,029,654.

Japanese published patent applications nos. 62-56141, 63-227318,63-75516 and 1-51359 each describe phased or offset sprockets for use intransmission or in a transfer case for a four-wheel drive vehicle. Thesepublications do not disclose engine timing systems. Moreover, theseprior art applications differ from the transmission and transfer caseapplications of the present invention in which phasing is utilized inconjunction with random or hybrid chains. The published Japaneseapplications teach the use of a "cancellation effect," which isdeveloped by the particular spacing of two offset sprockets. The"cancellation effect" differs from randomization in its approach to theproblem of chain noise. Cancellation relies on a pair of sprocketsoffset by 1/2 pitch in conjunction with two non-random chains. Eachsprocket provides a repetitive pattern of discrete chain and sprocketcontacts which are phased by 1/2 pitch and therefore act to "cancel" oneanother. In contrast, the random chain in the transmission embodiment ofthe present invention provides a random pattern of contacts betweenchain and sprocket. Randomization is inconsistent with the concept ofcancellation through generation of a repetitive pattern of discretecontacts.

The Japanese prior art applications do not utilize phasing inconjunction with an engine timing system. Timing systems applicationsinclude load fluctuations and extreme center distances that differdramatically from transfer case applications.

One embodiment of the present invention seeks to provide a phasingrelationship by using a silent chain construction having randomizationachieved by use of a combination of single toe inverted tooth links withconventional two toed inverted tooth links in a single chain assembly orin a double chain assembly. The combination of single toe links and twotoed links can randomize or alter the pattern of link and sprocket toothcontacts in the chain and sprocket assembly. The single toe links areprovided in a chain assembly with a split sprocket having a phasedrelationship, or a non-phased relationship.

Prior art chains have utilized single toe links, but not in a dual chainor phased chain assembly relationship. For example, U.S. Pat. No.959,046 discloses a single toe guide link. However, the guide links actonly to maintain the chain assembly on the sprockets. The guide links donot provide direct power transfer to or from the sprocket and thus donot impact the sprocket at the chain mesh frequency. Hence, the use ofsingle toe guide links does not effect the noise spectrum produced bythe sprocket tooth contacting links or articulating links.

U.S. Pat. No. 579,742 discloses a chain with single toe links that arelocated slightly off-center. The links engage the sprocket throughantifriction balls that are trapped in sprocket cavities. All of thelinks of the chain have single toes.

U.S. Pat. No. 637,056 shows a chain with single toe links that aresubstantially centrally located. The patent discloses a chain havingcylindrical sprocket teeth that come into contact with the link toe atits base. The contact of the link and the cylindrical toe is intended tooccur on both sides of the toe. All of the links of the chain are singletoe.

As part of the phased chain and sprocket assembly, the present inventionalso provides a modified sprocket construction. The modified sprocketmay be used with the random or hybrid chain assemblies, or with thesingle toe link chain assembly, to provide the phased chain and sprocketrelationship. The single toe links and sprocket are utilized in anattempt to modify the pattern of contacts between the chain and thesprocket and minimize problems of interference of the links with thesprocket as the links move off of the sprocket teeth.

SUMMARY OF THE INVENTION

The present invention relates to phased chain assemblies or systems.That is, transmission, transfer case or engine timing systems in whichthe sprockets are split into two portions or separate assemblies and theportions are offset or phased with respect to one another, with singleor multiple chains.

The present invention is directed to providing a phased relationshipbetween a pair of chain assemblies and a pair of sprockets in a chainsystem. The phasing is provided to modify the impact generated noisespectrum as well as the chordal action generated noise spectrum. Thephasing of the present invention involves modifications to the chainconstruction, the sprocket construction, and the relationship betweenthe positioning of the chain assemblies and sprockets.

Phasing the chain and sprocket relationship can reduce the number ofchain link teeth (or mass) impacting the sprocket during a given timeincrement. Similarly, phasing the chain and sprocket relationship canalter or phase the chordal action or articulation of the chain andsprocket. The chain randomization and sprocket phasing modifications canalter the impact and chordal action generated sound patterns.

The phasing of the present invention is achieved by modifications to thechain assemblies as well as modification to the sprockets. Themodifications to the sprockets include the use of split sprockets whichare phased by one-half tooth, or one-half pitch. The modifications tothe chain assemblies include randomization or the use of single toelinks in a single assembly or dual chain assemblies.

In one embodiment of the present invention, the sprockets of an enginetiming system are split into two portions and the portions are offset orphased with respect to one another. The engine timing system includesone driving sprocket located on the crankshaft and one driven sprocketlocated on the camshaft. Rotation of the crankshaft causes rotation ofthe camshaft through the chain and sprocket system. The crankshaftsprocket has one-half the number of teeth of the camshaft sprocket. Thecrankshaft sprocket and camshaft sprocket are each split and offset byone-half pitch. Two side-by-side chains are placed on the sprockets inthe phased relationship. One or both chains may be a random chain, asdescribed below.

In another embodiment of the present invention, the engine timing systemconnects the crankshaft with two overhead camshafts by a pair of chains.The crankshaft includes two sprockets, which are phased. Each chain isconnected to a single sprocket on each of the two overhead camshafts.Alternatively, each of the sprockets on the overhead camshafts is splitand phased, which requires four sprockets on the crankshaft. Two of thefour sprockets can be phased by one-half pitch from the other twosprockets, or all four sprockets can be phased by one-quarter pitch. Thechain systems-will include tensioners on the slack side of each chain tomaintain chain tension and snubbers on the tight side of each chain tocontrol chain movement during operation.

In another embodiment of the present invention, a timing systems has two(or dual) overhead camshafts for each bank of cylinders. The dualcamshafts on a single bank can both be rotated by connection to the samechain. Alternatively, the second camshaft can be rotated by anadditional camshaft-to-camshaft chain drive. The cam-to-cam drive chaincan also include single or dual tensioners for chain control. Eachsprocket in the system is split into two sprockets, which are phased oroffset.

In the various embodiments of the present invention, each singlesprocket is replaced by a pair of sprockets that are phased by one-halfpitch. Alternatively, the single sprocket can be replaced by threesprockets that are phased by one-third pitch, and then utilized withthree chains. Other modifications of number of sprockets and degrees ofphasing are possible and within the scope of the present invention.

In some embodiments of this invention, which specifically relate totransmissions or transfer cases, one or two random (or hybrid) chainsare provided with the split sprocket having one side phased one-halftooth ahead of the adjacent side. The random, or hybrid, chain includeslink sets of two different configurations, or links of a first set beingdifferent from links of a second set. The links of the two link sets maydiffer in contour, flank configuration, leading inside flankconfiguration, outside flank configuration, orientation (as withasymmetrical links), type of driving contact with the sprocket teeth orother types of randomization. The term contour refers to the overallshape or outline of the perimeter of the link.

Such an embodiment phases the impact noise spectrum by randomization andhaving effectively one-half of the teeth impacting the sprocket toothduring a given time increment, in comparison to a single chain of theextended width of the two chain assemblies. This embodiment also phasesthe chordal action of the chain by having the pins of the two chainsoffset by one-half pitch. The randomization enhances the effect of thesprocket phasing on the impact and chordal action generated noisespectra.

In another embodiment of this invention, one or two random or hybridchains are provided with a split sprocket having one side phasedone-half tooth ahead of the other side, and the sprocket teeth beingrandomized. The randomization of the sprocket teeth may be in anymanner, such as variable spacing, relieved teeth or tooth elimination.

Each of these embodiments, as well as certain other embodiments, mayinclude a plurality of chain assemblies, including assemblies of two,three, or four chain strands. Additionally, the sprockets may be phased1/4, 1/3 or 1/2 tooth, as well as various other amounts of pitch.Moreover, the dual chain assemblies may be spaced along the shaft, andnot necessarily part of a split sprocket. In such a configuration, caremust be taken to assure that the sprockets are tightly splined withrespect to the shaft to allow phasing of the chordal action.

Further, modifications may also be made to the chain assemblies. In oneembodiment of the present invention, randomization is achieved byproviding two chain assemblies of differing pitch. In another embodimentof this invention, randomization of the chain assembly is achieved by acombination of links having a pair of depending toes and links having asingle depending toe. In another embodiment, the chain assembly includesa lacing having fewer links in the guide link rows than in the non-guidelink rows.

In another embodiment of the present invention, an effort is made tomatch the load on the two chains in the phased system. As the differencein center distances between the two chains approaches zero, the loadcarried by each chain approaches an equal value. By matching the centerdistances, the load is more equally shared and each chain wears atapproximately the same rate.

In each chain assembly, the links are interleaved to form sets of links.Each link includes a pair of apertures, with an aperture from one set oflinks being aligned for interlacing with an aperture from an adjacentset of links. Pivot means, in the form of round pins or rocker joints,are utilized to connect the adjacent sets of links through theapertures, and to allow pivoting of the sets of links with adjacentsets. Guide links are placed on alternating sets to maintain thealignment of the chain on the sprockets.

The chain assembly of the embodiment having single toe and two toe linksutilizes the two different links in link sets or ranks extending acrossthe width of the chain. The links are arranged in patterns by sets inorder to modify the pattern of contacts of the links with the sprocketteeth. Thus, set by set or in a single set of the single toe links chainassembly, one or more two toed links may be followed in series by one ormore single toe links, which are followed by one or more two toed linksto complete the set across the width of the chain.

In the columns of links extending along the longitudinal length of thechain assembly, some columns consist solely of links with two dependingtoes and other columns consist solely of links with a single toe. In oneembodiment, the two toed links and single toe links are placed incolumns in the chain and a particular column of links running down thelength of the chain will include either two toe links or single toelinks. In one specific embodiment, a plurality of columns of two toedlinks are formed on the outside of the width of the chain with thesingle toe links being in a column or plurality of columns on the insideof the width of the chain. The single toe links in the center act as aninside guide link to maintain the chain along the sprockets. Thus, theuse of flanking guide links on the outer edge of the chain may beeliminated in some embodiments. The toes of the single toe links may belocated symmetrically with the center of the link or may be locatedslightly offset or asymmetrical with the center of the link.

In another embodiment of the present invention, a chain and sprocketassembly includes a split sprocket and two chains in side-by-siderelationship on the sprocket. One chain of the chain assembly isassembled with single toe links. The second chain of the assembly isassembled with conventional two toed links.

In this embodiment, the sprocket is split and constructed to accommodatethe first chain, or chain assembly portion, with single toe links on oneside and the second chain, or chain assembly portion, with two toedlinks on the other side, and the sprocket teeth of one side are phasedapproximately one half space ahead of the other side. In such a chainassembly, the point of articulation of one chain is approximately onehalf space ahead of the other chain. Alternatively, the sprocketportions are not phased but the teeth are aligned.

This embodiment may be combined into a single chain assembly, as in theearlier described embodiments. In such a composite chain assembly, thesingle toe links are on one side along the length of the chain and thetwo toed links are on the other side along the length of the chain. Thecomposite chain assembly would be utilized with the split sprocket.

Use of silent chain assemblies and sprockets constructed in accordancewith the teachings of the present invention is expected to result in thegeneration of noise patterns that are modified in comparison with thenoise patterns generated by a chain and sprocket assembly that does notutilize phased chain and sprocket relationships. The chain assembly ofthis invention is suitable for use in a variety of types of chainassemblies and with a variety of sprocket tooth forms.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the invention, one should refer tothe embodiments illustrated in greater detail in the accompanyingdrawings and described below by way of examples of the invention. In thedrawings, which are not to scale:

FIG. 1 is a side elevational view of a portion of the chain assembly ofone embodiment of the present invention, illustrating two types of linksinterconnected by a round pivot means;

FIG. 2 is a top plan view of a portion of the chain of FIG. 1;

FIG. 3 is a perspective view of a portion of a sprocket for use withchain assemblies of the present invention;

FIG. 4 is a perspective view of an alternate embodiment sprocket for usewith chain assemblies of the present invention;

FIG. 5 is a sectional view of the chain assembly taken along the line5--5 of FIG. 2;

FIG. 6 is a sectional view of the chain assembly taken along the line6--6 of FIG. 2;

FIG. 7 is an exploded view of a portion of the chain assembly showingone pattern of assembly of the links of the chain;

FIG. 8 is a side elevational view of a two toed link of the chain;

FIG. 9 is a side elevational view of a single toe link of the presentinvention;

FIG. 10 is a side elevational view of an alternate embodiment of asingle toe link of the present invention, having the tooth slightlyoffset from the vertical centerline of the link;

FIG. 11 is a side elevational view of a chain assembly of two toed linksfor use in conjunction with an assembly of single toe links; and,

FIG. 12 is a side elevational view of a chain assembly of single toelinks for use in conjunction with the assembly of two toed links of FIG.11.

FIG. 13A is a side elevational view of the single toe link of oneembodiment of the present invention;

FIG. 13B is a side elevational view of the two toe link of oneembodiment of the present invention;

FIG. 14 is a side view of one embodiment of the chain of the presentinvention having single toe links and two toe links;

FIG. 15 is a sectional view of the chain taken along line A--A of FIG.14;

FIG. 16 is a side view illustrating the chain and sprocket contacts ofthe chain of FIG. 14;

FIG. 17 is a side view of a dual sprocket assembly having the twoportions phased by one-half pitch and the teeth offset;

FIG. 18 is a sectional view illustrating the two portions of the chainassembly and the two portions of the sprocket assembly;

FIG. 19 is a side view illustrating the three types of links in thechain of FIG. 18;

FIG. 20 is a side view illustrating the interleaving of the three linksof FIG. 19;

FIG. 21A is a side view of a section of links having single toes;

FIG. 21B is a side view of a link having a single toe;

FIG. 22A is a side view of a section of links having double toes;

FIG. 22B is side view of a link having two toes;

FIG. 23 is a side view of a sprocket for the chain assembly of the linksof FIGS. 21 and 22, showing the sprocket for the links of FIG. 21 inphantom, with the teeth aligned.

FIG. 24 is a sectional view of a pair of sprockets in spaced apartposition on a shaft;

FIG. 25 is a top view of a pair of chains of offset by one half pitch;

FIG. 26A is a side view of a link having straight inside flanks;

FIG. 26B is a side view of a link having curved inside flanks;

FIG. 27A is a side view of a link having a first pitch length;

FIG. 27B is a side view of link having a second pitch length;

FIG. 28 is a schematic illustrating a timing chain system with a singlecamshaft and crankshaft;

FIG. 29 is a schematic illustrating a timing chain system with singleoverhead camshafts;

FIG. 30A is side view of a timing chain and camshaft sprocket;

FIG. 30B is a top view of the chain system of FIG. 30A, illustrating theoffset of the two chains;

FIG. 31 is a sectional view along line A--A from FIG. 30A;

FIG. 32A is a side view of a timing chain and crankshaft sprocket;

FIG. 32B is top view of the timing chains of FIG. 32A, illustrating theoffset of the four chains;

FIG. 33 is sectional view along line C--C from FIG. 32A;

FIG. 34 is a schematic illustrating the positioning of the two camshaftsand a single crankshaft and four chains;

FIG. 35 is schematic illustrating a timing chain system with dualoverhead camshafts and a camshaft-to-camshaft drive system;

FIG. 36 is a schematic illustrating a timing chain system with dualoverhead camshafts and a single chain system for each cylinder bank;

FIG. 37 is a top view of a chain with block laced construction;

FIG. 38 is a side view of the chain of FIG. 37;

FIG. 39 is a top view of a timing chain illustrating a lacing pattern;

FIG. 40 is a top view of a timing chain illustrating a lacing pattern;

FIG. 41 is a schematic illustrating an example of phased sprockets forsingle overhead camshafts;

FIG. 42 is a top view of a chain illustrating a lacing pattern;

FIG. 43 is a side view of the chain of FIG. 42.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS PHASED CHAINASSEMBLIES

Turning now to the drawings, the present invention is directed toproviding phasing of chain assemblies and associated sprockets. Thephasing is provided to modify the impact generated noise spectrum aswell as the chordal action generated noise spectrum.

The present invention modifies the impact sound spectrum by modifyingthe pattern of impacts of the chain link teeth with the sprocket teeth.In a conventional chain assembly, where the links of a particular set orrow of links are of identical configuration or identical pitch, theflanks of the teeth of the links in the row all contact the sprocketteeth at approximately the same instant. In a random or hybrid chainassembly, the links sets include links of different configuration,contours, orientations or pitch. Examples of links from random chainsare shown in FIGS. 26A and 26B, where the inside flanks of the two linksdiffer in configuration, and in FIG. 27A and 27B, where the pitch P1 ofone link differs from the pitch length P2 of the other link. The insideflanks of the link in FIG. 26A are substantially straight while theinside flanks of the link in FIG. 26B are curved. In a random chain theflanks of the teeth of the links in the same row all contact the teethof the sprocket at approximately the same time or instant, but thepattern of link and sprocket teeth contacts is modified as between thesets. By phasing, or modifying, the timing or mass of chain linkscontacting the sprocket during a particular instant or time increment,the impact sound generated by the chain and sprocket contacts may befurther lessened and the pure sonic tones generated by the contacts mayalso be lessened or avoided.

The present invention provides impact phasing in a number of differentways. In a number of the described embodiments, the chain assembly isdivided into several portions and the sprockets for each portion arephased or adjusted by one-fourth, one-third or one-half tooth space withrespect to the adjacent portion of the chain assembly. In this manner,the mass of links contacting the sprocket during the given timeincrement is lessened and the repetition of contacts is furthermodified.

The present invention also phases or modifies the chordal action of thechain and sprocket in order to modify the sound pattern or spectrumgenerated by the chordal action. Chordal action occurs as the chain linkenters the sprocket from the free span of the chain. The link is pivotedwith respect to the free span as the link contacts the sprocket toothand begins to enter and seat in the sprocket. Chordal action generatesmovement of the chain in a direction perpendicular to the linearmovement of the chain and generates an objectional pure sonic tone.Chordal action causes a speed variation in the linear movement of thechain, which results in a tension variation on the sprockets.

The present invention provides chordal action phasing in a number ofways. In the embodiments where the random chain assembly is divided intoseveral portions and the sprockets placed in phased relation betweenthose portions, the chordal action of the chain is phased by thelocation of the pins in each portion of the chain assembly. By havingthe pins offset in adjacent portions of the chain, which a result of thephasing of the sprocket teeth, the chordal action of the chains enteringthe sprocket teeth is phased with respect to adjacent portions of thechain assembly. FIG. 25 illustrates the two separate chain assemblieswhere the pins of the two chain assemblies are offset by one half pitch.

In some embodiments of the present invention, only the impacts betweenthe chain links and the sprocket are phased. In other embodiments, onlythe chordal action between the chain assemblies and the sprockets isphased. In some embodiments, both the impacts and the chordal action arephased.

FIG. 1 illustrates a portion of one embodiment of the chain assembly ofthe present invention generally at 10. The chain assembly may be of ahybrid or random type in which links are provided in two different typeof link sets, such as shown in U.S. Pat. No. 4,342,560, which isincorporated herein by reference. Examples of links from random chainsare shown in FIGS. 26A, 26B, 27A and 27B. The chain shown specificallyin FIG. 1 is a species of the present invention which includes link setshaving links with two inverted teeth and links with a single invertedtoe, which is described in more detail below.

The chain assembly includes sets 12, 14 or ranks of links, which areshown more clearly in FIG. 2. A single set or row of links extendsacross the width of the chain and includes several interleaved links.The sets are then interleaved with adjacent sets to form the endlesschain assembly.

The chain assembly is utilized to drive, for example, an engine timingassembly including a camshaft (not shown) and crankshaft (not shown), ora transfer case for four-wheel drive vehicles. On the shafts are mountedsprockets, such as the sprockets 18, 19 shown in FIGS. 3 and 4. Thesprockets provide the means of power transfer between the chain and thetwo shafts. The sprocket 19 of FIG. 4 is split into two portions 86, 88,which are phased or off-set by one-half tooth space. The sprocket 18 ofFIG. 3 is split into three portions 70, 72, 74 which are off-set byone-half tooth space. Alternatively, the portions of sprocket 18 may beoff-set by one-third tooth space for each section of the sprocket.

The sprocket portions may be located adjacent to each other, and formedof a single piece or fused together. Alternatively, the sprocketportions may be separated and spaced apart across the length of theshaft. However, care must be taken when the sprockets are spaced apartthat the sprockets are splined tightly to the shaft. Any excesstolerance between the sprocket and the spline will defeat the chordalaction phasing of the assembly. FIG. 24 illustrates portions of each oftwo sprockets that are splined to a shaft. The sprockets are shown inseparate and spaced apart relation.

In one embodiment of the present invention, a pair of hybrid or randomchain assemblies, that is, a chain assembly having link sets with linksof differing contour, configuration, orientation or pitch, are utilizedwith the phased sprocket portions 86, 88 of FIG. 4. By phasing thesprocket portions one-half tooth space, both the impact and the chordalnoise spectra are phased. The randomization of the links of the chainwill further modify the impact and chordal action sound spectra, whichis expected to result in chain of lower noise than a conventional chainand sprocket assembly. In a second embodiment, three random chainassemblies are utilized with the phased sprocket portions shown in FIG.3 or with three sprocket portions that are phased one-third tooth space.Additional similar embodiments are possible where additional randomchains are utilized with additional sprocket portions, and the phasingrelationship of the sprocket portions is altered to differing toothspace relationships.

In another embodiment of the present invention, the above-describedrandom chain is utilized with random or hybrid sprockets as the phasedsprockets. The hybrid sprocket utilizes unevenly spaced teeth. Thespacing of the teeth is modified by relieving certain portions ofcertain teeth, or by changing the configuration of the flanks of thesprocket teeth. The hybrid sprocket may be used with a standard sprocketor in pairs of hybrid sprockets in combination with any of theabove-described embodiments.

In another embodiment of the present invention, randomization isachieved by using the sprockets of FIGS. 3 and 4 are with two chains ofdifferent pitches. For example, a 3/8 inch pitch chain may be used withsprocket portion 86 of FIG. 4 and a 1/2 inch pitch chain may be usedwith the sprocket portion 88 of FIG. 4. The use of chains of differingpitch further randomizes or modifies the pattern of contacts between thechain and sprocket and thus modifies the impact and chordal actiongenerated sound spectra. The sprockets are phased by the use ofdiffering number of teeth on the sprockets to match the chains ofdiffering pitch.

In another embodiment of the present invention, the center distances ofthe two chains of the phased chain system are matched as closely aspossible. The matching of center distances can be utilized in any of theother embodiments described in this application. The center distancesare matched in an effort to match the loading of the two chains in thephased system.

As the two chains in the system are operated, the chain which carriesthe higher load will tend to wear at a faster rate than the chain withthe lower load. The greatest variation in sharing of load occurs at thelowest torque applications of the system. Moreover, the chain with theshortest center distance tends to transmit the greatest load, or carry adisproportionate share of the load.

In the present invention, the center distances of each chain are matchedas closely as possible in an attempt to equalize the wear rates of thetwo chains. As the difference in the center distances of the two chainsapproaches zero, the load is more equally shared between the chains andthe wear rates match more closely.

While the sprockets of the two chain assemblies may each be fixed onparallel shafts, the center distance of each chain assembly depends onthe chain length, pitch, sprocket size, and manufacturing tolerances. Ifthe chain length, pitch and number of teeth on each sprocket are known,then the center distance may be determined from standardized tablesknown in the art. The number of teeth on the sprockets may vary as, forexample, when driving between a large and a small sprocket. The presentinvention attempts to match the center distances of the two or morechains in the phased system as closely as possible within manufacturingtolerances.

In operation, the chain assembly of the present invention modifies thepattern of contacts of the chain with the sprocket. The impacts of thelinks with the sprocket are modified by use of the random chain with thephased sprockets in the chain assembly. Additionally, the chordal actionof the sprockets will be altered and reduced on account of themodification of the chain mesh with the sprocket. Modification of thechain and sprocket assembly in the described manners will result in amodification of the pattern of contacts which will modify the noisespectrum for the chain.

Use of a chain assembly or a sprocket constructed in accordance with theteachings of this invention is expected to result in the generation of anoise pattern that is modified in comparison with the noise patterngenerated by a chain and sprocket in which all of the links are ofidentical configuration and no phasing relationship is present betweenthe sprockets of the assembly. The chain assembly of this invention issuitable for use with a variety of chain types and sprocket tooth forms.Of course, some patterns of combinations of chain assemblies andsprocket phasing relationships will provide less objectionable noisecharacteristics than other combinations.

HYBRID CHAIN ASSEMBLY WITH SINGLE TOE LINKS

In another series of embodiments of the present invention, the phasingis accomplished by the combination of single toe and two toed links inthe chain assembly. The combination may be included in a single assemblyor by having the two portions of the assembly in conjunction with thesplit sprockets shown in FIGS. 3 and 4. The species of the inventionshown in FIG. 1 includes the single toe links and two toed links in sets12 and 14.

Some sets of links, those designated as set 12, may also includeflanking guide links 20 along their outside edge. The guide links 20 areincluded in every other set of links and act to maintain the chainassembly on the sprockets. The guide links do not include any dependingmembers or teeth for contacting the sprockets. An inside guide link mayalso be used, in which case a groove is provided in the sprocket tomaintain the position of the guide link. With certain embodiments of theinvention, as shown below, the center links act as center or insideguide links, and thus outside flanking guide links are not necessary tomaintain the alignment of the chain on the sprockets.

The sets 12, 14 of links also include interleaved driving links 22, 24or inverted tooth links. The inverted tooth links are provided in anumber of forms or configurations, as shown in FIGS. 7, 8, 9, and 10.The two toed links 22, shown in FIG. 8, are known in the prior art, andare utilized in the previously described random chain embodiments. Thelinks 22 have a pair of apertures 28, 29 and a pair of depending toes30, 32. The toes are defined by outside flanks 34, 36 and inside flanks38, 40. The inside flanks are joined at the crotch 41. The inside andoutside flanks of link 22 can have a number of configurations, includingstraight or arcuate. The link can be symmetrical about a verticalcenterline between the apertures 28, 29 or can be asymmetrical about thecenterline.

The single toe links of the present invention include the links 24 and26, shown in FIGS. 9 and 10. The link 24, shown in FIG. 9, has a pair ofapertures 42, 44, but only a single depending toe 46. The toe 46 has twoflanks 48, 49, of which one or both can be designed for contact with thesprocket teeth. Alternatively, the single toe can be designed forcontact with the root of the sprocket and therefore to avoid contactwith the sprocket teeth. The flanks can be any number of configurations,including straight or arcuate, and can be designed to contact or toavoid contact with the sprocket teeth.

The link has a pitch 50 measured between the centers of the apertures42, 44. The tooth height 52 is measured from the horizontal centerlineto the base of the toe 46. The tooth is constructed to minimizeinterference with the sprocket teeth as the tooth is coming off of thesprocket. The tooth geometry is calculated on the basis of number ofteeth, pitch, tip radius, flank contact radius, toe height and toothangle, and the acceptable amount of interference.

The single toe link 26, shown in FIG. 10, has a pair of apertures 56,58, and a single depending toe 60. The toe is located asymmetrically orslightly offset with respect to the vertical link centerline between theapertures. The toe includes two flanks 62, 64 for contact with thesprocket. As in the other link embodiments, the flanks can be any numberof configurations, including straight or arcuate, and can be designedfor contact with or to avoid contact with the sprocket teeth.

The sets of interleaved links 22, 24, 26 are shown in FIGS. 1, 2 and 7.The sets may include mixtures of links 22 and 24, or links 22 and 26, ormixtures of all three types of links and additional links. As shown inFIG. 2, and detailed in the sectional views of FIGS. 5 and 6, a set oflinks across the width of the chain is formed of a number of two toothedlinks 22 and single toe links 24. As shown in FIG. 7, a column of linkscan include a number of interleaved two toed links 22, as in columns 67and 68. An interleaved column 69 can include a number of interleavedsingle toe links 24.

In assembling the chain in the embodiment shown in FIG. 7, the columns67, 68 of two toed links are formed by a conventional lacing of rows oflinks 22. Similarly, the column 69 of single toe links is formed by aconventional lacing of rows of single toe links 24. The columns 67, 68,69 are then combined to form the chain assembly. In this manner, thesingle toe links 24 are placed between the two toed links 22. As aresult of the combination in the assembly, the single toe links may actas an inside guide link, and the use of outside guide links 20 may beavoided in this embodiment.

In the embodiment shown in FIG. 7, the single toe links 24 are of thetype shown in FIG. 9. That is, the single toe 46 is centrally locatedbetween the two apertures of the link. In a second embodiment, thesingle toe links are of the type shown in FIG. 10. That is, the singletoe 60 is slightly offset from the vertical centerline of the linkbetween the two apertures. In this second embodiment, the single toelink 26 may also act as an inside link which avoids the need forexternal guide links 20.

In the embodiment shown in FIG. 7, a column 67 of two toed links has asingle link 22a interleaved with link 22b, which is interleaved with asingle link 22c. Similarly, in column 68 on the opposite side of thechain, a single link 22d is interleaved with link 22e, which isinterleaved with link 22f. In the center column of single toe links, asingle link 24a is interleaved with two links 24b and 24c, which areinterleaved with a single link 24d. The above-described lacing patterncontinues along the entire length of the chain.

In another embodiment, certain of the links in FIG. 7 are altered inorder to provide alternate lacing patterns. For example, either links24b or 24c may be replaced in the lacing pattern with two toed links 24.Many other patterns and combinations of single toe and two toed linksare possible that are within the scope of the present invention.

FIGS. 5 and 6 illustrate the expected contacts of the links of the chainFIG. 7 with the sprocket teeth as the chain enters the sprocket duringoperation. Some or all of the flanks of the two toed links and theflanks of the single toe links may contact the sprocket teeth. The exactcontacts will be dependent on the configurations of the links and thearrangement of the links in the chain assembly. Alternatively, thesingle toe link can be designed to avoid contact with the sprocket teethand only contact the root of the sprocket.

As shown in FIG. 3, the modified sprocket is also provided for use withthe assembly of FIGS. 5, 6 and 7. As previously explained with regard tothe other embodiments, the sprocket 18 is provided with three layers 70,72, 74, with each layer having spaced sprocket teeth 76, 78, 80. Thesprocket teeth are staggered in order to mesh with the combination ofsingle toe and two toed links in the chain assembly of FIG. 7. Thesprocket can be any number of layers in order to conform to the columnsof two toed links or single toe links that are provided in the chainassembly, but is preferably of three layers with the center layer offsetby one-half tooth space. The layers may be formed as a laminate and thencombined together to provide the sprocket. In the combining of the threelayers, the sprocket teeth of one layer can be staggered with respect tothe teeth of another layer. Thus, each layer can be staggered byone-third pitch. The single toe links chain assembly of the presentinvention is capable of use with any number of configurations ofsprockets, and is not limited to use with the sprocket of FIG. 3.

Another embodiment of the present invention is shown in FIGS. 11 and 12in which a chain assembly comprises a combination of two chainassemblies in side-by-side relation. This embodiment combines theabove-described embodiments of dual chain assemblies and phasedsprockets with the embodiments of chains with single toe links. Thefirst chain assembly 82 is preferably formed entirely of single toelinks. The second chain assembly 84 is preferably formed entirely ofconventional two toe links, such as links 22g, 22h, 22i, 22j. The chainassembly 82 of single toe links may include the links 24 of FIG. 9 withthe toe centrally located, such as links 24e, 24f, 24g, 24h. Pinsinterconnect the links of the separate chain assemblies.

The split sprocket 19 is provided for use with the embodiment of twochain assemblies as shown in FIG. 4. The sprocket is constructed withthe sprocket teeth of one side 86 indexed one half space ahead of theteeth on the other side 88 of the sprocket. In this manner, the point ofarticulation of one chain assembly is approximately one half space aheadof the other chain assembly.

Another embodiment of this invention is shown in FIGS. 13, 14, 15 and16. This embodiment includes the chain assembly in two portions. Theportions are either separated and spaced apart or combined into a singlechain assembly. As shown, in FIG. 15, the chain can be a single assemblywith pins 99 extending through the entire width of the chain. Oneportion of the chain assembly utilizes the single toe links 100, shownin FIG. 13A, which have a single toe 101 centrally located between theapertures 102, 104. The second portion of the chain assembly utilizesthe conventional double toe links 106, illustrated in FIG. 13B. If thechain assembly is split into two portions, then the pins are aligned.

The chain assembly is shown in a side view in FIG. 14. As shown in FIG.14, in this embodiment, the single toe 101 is longer than the toes 107of the double toe link 106. The assembly is shown in sectional view inFIG. 15. The sectional view illustrated the central location of thesingle toe 101 and the locations of the two toes 107 of the double toelink 106.

The chain assembly is shown in relation to a sprocket 110 in FIG. 16.FIG. 16 illustrates the expected contacts of the chain with the sprocketteeth. As shown, the longer single toe 101 will seat deeper in thesprocket by positioning both flanks of toe 101 against the sprocketteeth.

Another embodiment of the present invention having phased sprockets isshown in FIGS. 17, 18, 19, and 20. As shown in FIG. 18, the chainassembly is split with the first portion 112 and the second portion 114phased by one-half pitch. The phasing is accomplished by offset of thetwo sprocket portions 116, 118 by one half tooth, as shown in FIG. 17.The chain assembly is constructed of three link types, that is, innerlinks 120, inner guide links 122 and outer guide links 124. Thepreferred embodiment of this construction utilizes a rocker joint, whichincludes an hour-glass shaped aperture 126 and a pair of pivot pins 128,130. The aperture and pins are shown in U.S. Pat. No. 4,911,682, whichis incorporated herein by reference.

The lacing pattern for the embodiment of FIG. 9, across the width of thechain, includes a single inner guide link 122 in the center and a pairof outer guide links 124 on each side. Between the inner guide link 122and outer guide links 124 are a plurality of inner links 120. The innerlinks may be of identical configuration or may be randomized. The outerguide links 124 include a pair of depending toes which are constructedfor contact with the sprocket teeth. The outer guide link includes anaperture 132 that provides a press fit with the pin 128. The outer guidelinks may be of identical configuration or may be randomized.

The inner guide link has a flat bottom 134 that does not include acrotch. The flat bottom is designed to ride in a groove 136 cut in thesprocket. The inner guide link maintains the chain assembly in itslocation on the sprocket. The inner guide link includes apertures 138that allows articulation of the link with respect to the pins. The innerlink 120 also includes an aperture 126 that allows articulation of thelinks with respect to the pins. The outer guide links have aperturesthat receive the pins in a press fit and thus do not allow articulationof the pins with respect to the links.

This construction of inner and outer guide links provides severaladvantages. For one, the inner guide link 122 lacks a crotch and thus isinherently stronger than the links having inverted teeth separated by acrotch. Second, the outer guide link, with the pins being press fit, isstronger than the links having apertures that allow articulation of thelink with respect to the pins. The use of the stronger guide links allowfewer links in the guide rows in the lacing pattern to achieve the samestrength chain. Fewer links in the guide rows allows a minimization ofthe number of links in the chain.

Additionally, the outer guide links 124 include inverted teeth that areconstructed for contact with the sprocket teeth. The use of invertedteeth on the outer guide links allows more links to contact the sprocketthan in similar chain having outer guide links that do not contact thesprocket. In this manner, for a given number of links in the chain, andwidth of chain, a greater number of links contact the sprocket. Theembodiment shown in FIGS. 18, 19 and 20 may be used as a separate chainassembly, without the phased sprockets, and will achieve several of theadvantages noted above.

Another embodiment of the present invention is shown in FIGS. 21, 22,and 23. The embodiment includes two chain assemblies, or a chainassembly having two separate portions. One portion of the assembly,shown in FIGS. 21A and 21B, utilizes single toe links 140. The otherportion of the assembly, shown in FIGS. 22A and 22B, utilizes double toelinks 142. The sprocket construction is a dual or split sprocket havingone portion 144 constructed for receiving double toe links and anotherportion 146 constructed for receiving single toe links.

The sprocket portions have their teeth aligned. In the single toe linkportion of the chain assembly, the pins 148 are centered over the teethof the sprocket. In the double toe link portion of the chain assembly,the pins 150 are centered between the teeth of the sprocket. In thismanner, the pins are offset and the chordal action of the two chainassembly portions is phased. However, the impact sound pattern of thetwo chain assembly portions is not phased, as the links impact thesprocket teeth in the two portions at substantially the same time.

In operation, the chain assembly of the present invention modifies thepattern of contacts of the chain with sprocket. The impacts of the linkswith the sprocket are modified by use of two toed and single toe linkswithin the chain assembly. With different types of links with differingnumbers of toes, the links will impact the sprocket teeth at varyingtime intervals. Additionally, the chordal action of the sprockets willbe altered and reduced on account of the modification of the chain meshwith the sprocket. Modification of the chain in the described mannerwill result in a modification of the pattern of contacts which willmodify the noise spectrum for the chain.

Use of a chain assembly or a sprocket constructed in accordance with theteachings of this invention is expected to result in the generation of anoise pattern that is modified in comparison with the noise patterngenerated by a chain and sprocket in which all of the links are ofidentical configuration and have the identical number of toes. The chainassembly of this invention is suitable for use with a variety ofsprocket tooth forms. Of course, some patterns of combinations of linkswill provide less objectionable noise characteristics than otherpatterns of links.

PHASED TIMING CHAIN SYSTEMS

Several embodiments of the present invention involve phased timingsystems. In these embodiments, engine timing systems have singlesprockets replaced by two or more sprockets or sprocket portions and thesprockets are offset or phased with respect to one another. Theseembodiments include a number of chain configurations, including chainlacing configurations especially useful for timing systems.

FIGS. 28 and 29 illustrate two configurations of the phased timingsystem of the present invention. FIG. 28, the engine timing system 200includes one driving sprocket system 202 located on the crankshaft 203and one driven sprocket system 204 located on the camshaft 205. Rotationof the crankshaft causes rotation of the camshaft through the chain 206and sprocket system. The crankshaft sprocket 202 has one-half the numberof teeth of the camshaft 204 sprocket. The camshaft typically controlsthe valve train operation through hydraulic lifters and rocker armsconnected to the valve stems.

In order to implement the phasing of the present invention, thecrankshaft sprocket and camshaft sprocket are each replaced by pairs ofsprockets 208, 210 that are offset by one-half pitch. Two side-by-sidechains 212, 214 are placed on the sprockets in the phased relationship.One or both chains may be a random chain.

In the embodiment illustrated in FIG. 29, the engine timing systemutilizes a crankshaft 216 connected to two overhead camshafts 218, 220by a pair of chain systems, 222, 224. If only the crankshaft sprocketsare phased, then two offset sprockets are placed on crankshaft in aphased relationship. Each chain 222, 224 is connected to a singlesprocket 228, 230 on each of the two overhead camshafts. If the camshaftsprockets are also phased, then two offset sprockets are placed on eachoverhead camshaft in a phased relationship. Four sprockets are then usedon the crankshaft. Four chains connect the four sprockets on thecrankshaft with the two sprockets on each camshaft. Two of thecrankshaft sprockets 232, 234 can be phased by one half pitch with theother two crankshaft sprockets, or all four sprockets can be phased byone quarter pitch. The chain systems include tensioners 236, 238 on theslack side of each chain to maintain chain tension and snubbers 240, 242on the tight side of each chain to control chain movement duringoperation.

The components of the phased timing system of FIG. 29 are shown in FIGS.30, 31, 32, 33 and 34. FIG. 30A shows a left bank sprocket system foroperating the overhead camshaft for the left bank of cylinders. Thesprocket system 228 is a split sprocket having a first portion 244 and asecond portion 246. The portions are preferably phased by one-halfpitch. The sprockets are secured to the left bank camshaft and cause itsrotation. Two chains 250, 252 are wrapped around the sprockets. Thechains may have any one of a number of lacing patterns, including randomlink lacing patterns. As shown in FIG. 30B, the pins of chains 250, 252are offset and nested.

A right bank sprocket system operates the right bank camshaft for theright bank of cylinders. The sprocket system also includes two sprocketswhich are offset or phased by one half pitch. The sprockets are securedto the camshaft for the right bank of cylinders. Two chains are wrappedaround the sprockets. The chains are offset by one-half pitch.

The crankshaft, shown in FIGS. 32, 33 and 34, includes four sprockets256, 257, 258, 259 for the four chains 250, 252, 260, 262. Two sprockets264, 266 are preferably offset by one-half pitch, and the remaining twosprockets 268, 270 are also offset by one-half pitch. All four chainsare stacked at the front of the engine, with the pins of the chainsnested to allow optimum packaging of the system.

The overall system, shown in FIG. 29, includes a pair of tensioners 236,238 to maintain the chain tension on the slack side of the chain, aswell as a pair of snubbers 240, 242 to maintain chain control on thetight side of the chain. The tensioners and snubbers include faceportions of extended width to accommodate the pair of chains operatingon each side of the system.

In the above-described system, the chains are phased by offsetting thesprockets by one-half pitch. Further phasing modification can be made bydetermining the initial contact point of each bank's timing chain andthen phasing the initial contact point by one-half pitch. Such anapproach attempts to phase the impact sound pattern by phasing theinitial contact point.

The initial contact point of a particular system will vary engine byengine and is dependent on the engine's geometry. Each bank of cylindersutilizes at least one chain assembly to operate the bank camshaft. Eachchain assembly is placed at an angle with respect to the vertical. Theangle is dependent on the engine geometry. As a result of this geometry,the two assemblies in a bank-to-bank system form an angle with respectto one another. Unlike a conventional transfer case or transmissionapplication, the chains are in a non-parallel relationship with respectto one another. The angle to the initial contact point of each bank canbe approximated by determining the angular difference between theentrance point (estimated as the tangent between the tight strand pitchline and the outside diameter of sprocket) and a reference line locatedat the center of the nearest tooth past the entrance point. This angulardifference provides an indication of the amount of phase inherentlyprovided in the geometry of the system. The initial contact point isdefined for purposes of the present invention, and the necessarygeometric relationships, to be the tangent between the tight strandpitch line and the outside diameter of the sprocket. The actual initialcontact of the teeth will depend on the link geometry as well as thepitch of the chain.

This angular difference provides an adjustment to the offset of thesprockets in order to provide a phasing of the initial contact points ofa specified, predetermined amount. Thus, for example, the right handbank crankshaft sprocket would be rotated by an amount equal to theangle to initial contact plus an amount equal to the desired offsetamount of the sprocket pitch length and then rotated in the reversedirection (subtract) an amount of the angular difference. The left bankcamshaft sprocket will then need to be rotated by half that amount toretain the initial cam timing. In this manner, the initial contacts ofthe chain assemblies with the sprockets are phased or offset by acertain portion of the pitch.

An example of phasing of initial contact points is illustrated in FIG.41, with reference to the phasing of a sprocket with twenty-one teeth.The distance of offset necessary to achieve phasing of one-half pitch ofa twenty-one tooth sprocket is 8.5714 degrees, which is shown in FIG.41. For the example of FIG. 41, which includes a pair of single overheadcamshafts on a 90 degree V-8 engine, the geometric layout finds that theentrance to the crankshaft of the right bank of cylinders is 13,633degrees from a reference line to the entrance line (rotation is in theclockwise direction). The reference line is located at the center of thenearest tooth that is past the entrance point. The entrance line isdefined to be the point of tangency between the tight strand pitch lineand the outside diameter of the sprocket. Using this same methodology,the entrance point to the crankshaft sprocket of the left bank ofcylinders is at an angle of 7.269 degrees from the reference line, asshown in FIG. 41.

From these two angles, the amount of phase between the two crankshaftsprockets is calculated to be 13,663-7.269=6.394 degrees. An angulardifference of zero means that the initial contacts are phased withrespect to one another as a result of the geometry of the system. Inorder to offset the sprockets by one-half pitch with respect to oneanother, the two sprockets must be phased by 8.571 degrees. Thus, inorder to phase the initial contacts, the right bank crankshaft sprocketmust be rotated clockwise by a total angle of:13.663+[8,571-6.394]=15.840 degrees.

In another embodiment of the present invention, the engine timingsystems has two (or dual) overhead camshafts for each bank of cylinders.The dual overhead camshaft timing systems are shown in FIGS. 35 and 36.In the system shown in FIG. 35, the first drive system is similar to thesingle overhead cam system shown in FIG. 29. The system adds a chaindrive, or camshaft-to-camshaft drive, to operate the second camshaft oneach bank of cylinders. Thus, chain 280 is wrapped about sprockets 282,284 and chain 286 is wrapped about sprockets 288, 290. In the cam-to-camdrive system, dual-acting tensioners 292, 294 are included to maintainthe chain tension.

In addition to the phasing of the crankshaft to camshaft drive, asdescribed above, the system of FIG. 35 includes phasing of thecam-to-cam drive. A single sprocket can be utilized on each camshaft andthat sprocket can be offset or phased with respect to the other camshaftsprocket that is driven by the crankshaft. Alternatively, the cam-to-camdrive can include a pair of sprockets on each camshaft that are phased,and then those sprockets are phased with respect to the other camshaftsprockets.

In this system, as described above, the crankshaft sprockets can beoffset to phase initial contacts of the chains. Additionally, theinitial contacts of the camshaft sprockets can be phased. Thus, theinitial contact of the chain system contacting the camshaft sprocketdriven by the crankshaft is phased with the initial contact of the chainsystem that is driving the second camshaft. These initial contacts canbe phased on both camshaft drives.

In the dual overhead cam system of FIG. 36, both camshafts on each bankof cylinders are driven by the same chain system. Thus, the system ofFIG. 36 expands the single overhead cam system of FIG. 29 by having anadditional camshaft on each bank, and the use of chain of greater centerdistance to drive both camshafts. Phasing is accomplished is the samemanner as described above.

In the various embodiments of the present invention, each singlesprocket is replaced by a pair of sprockets that is phased by one-halfpitch. Alternatively, the single sprocket can be replaced by threesprockets that are phased by one-third pitch, and then utilized withthree chains. Other sprockets are phased so that the initial impacts ofthe chains with the sprockets are phased. Additional sprockets may beused within the entire system. Other modifications of number ofsprockets and degrees of phasing are possible and within the scope ofthe present invention.

A number of different chain lacings are possible for use in the systemsof the present invention. A chain and lacing construction referred to asblock lacing is described in U.S. Pat. No. 4,758,210, which isincorporated herein by reference. A block lacing construction is alsoshown in FIGS. 37 and 38. Rows of inside or articulating links 300,which have inverted teeth constructed to contact the teeth of thesprocket, have the inside links formed in stacks or blocks 302. Rows ofinside links 300 are interleaved with rows of guide links 304, which donot have inverted teeth and are constructed to maintain the chain on thesprocket. The chain is constructed by repetition of this lacing, withthe inside links being all identical, or of different flankconfigurations.

FIG. 39 illustrates another type of lacing for use in the system of thepresent invention. Pair of inside links 310 are stacked and interleavedwith other stacked pairs of links 312. In the guide row 314, only twolinks are found, which are located in the center of the link. In thenon-guide row 316, four links are found, which are located outside ofthe aforementioned links of the guide row.

FIG. 40 illustrates another type of lacing for use in the system of thepresent invention. Pairs of inside links 318 are stacked and placed atthe outside of the lacing pattern in the non-guide row 320. These linksare then interlaced with single inside links 324 in both the guide 326and non-guide row 320. This lacing pattern is continued throughout thelength of the chain.

FIGS. 42 and 43 illustrate another type of lacing for use in the systemof the present invention. Pairs of inside links 330 are stacked inblocks in the non-guide row 332. Pairs of guide links 334 in the guiderow 336 are interlaced with the inside links. No inside links arepresent in the guide row. This lacing pattern is continued throughoutthe length of the chain.

While several embodiments of the invention are illustrated, it will beunderstood that the invention is not limited to these embodiments. Thoseskilled in the art to which the invention pertains may makemodifications and other embodiments employing the principles of thisinvention, particularly upon considering the foregoing teachings.

What is claimed is:
 1. A phased chain and sprocket assembly,comprising:first and second driving sprockets connected to a singledrive shaft, said first and second driving sprockets having a pluralityof spaced teeth, said driving sprockets being disposed in parallelrelationship along said drive shaft, the location of the teeth of saidfirst driving sprocket being offset with respect to the teeth of saidsecond driving sprocket, first and second driven sprockets connected toa single driven shaft, said first and second driven sprockets having aplurality of spaced teeth, said driven sprockets being disposed inparallel relationship along said driven shaft, the location of the teethof said first driven sprocket being offset with respect to the teeth ofsaid second driven sprocket, said drive shaft being operativelyconnected to a power input and said driven shaft being operativelyconnected to a power output, said first driving sprocket being alignedwith said first driven sprocket and having a first chain assemblydrivingly connecting said first driving sprocket with said first drivensprocket, said second driving sprocket being aligned with said seconddriven sprocket and having a second chain assembly drivingly connectingsaid second driving sprocket with said second driven sprocket, saidfirst and a second chain assemblies having a plurality of interleavedsets of inverted tooth links, said links being adapted to contact theteeth of at least one of said sprockets, pivot pins connecting adjacentsets of links, each link defining apertures for receiving said pivotpins, said first chain assembly having some sets of links of a firstconfiguration and other sets of links of a different configuration, saidsome sets of links being arranged in a prescribed pattern with saidother sets of links.
 2. The chain and sprocket assembly of claim 1wherein said links of said first chain assembly impact the teeth of saidfirst driving sprocket at a first chain mesh frequency, said links ofsaid second chain assembly impact the teeth of said second drivingsprocket at a second chain mesh frequency, said first chain meshfrequency being shifted in time with respect to said second chain meshfrequency.
 3. The chain and sprocket assembly of claim 2 wherein saidfirst chain mesh frequency is variable and said second chain meshfrequency is substantially constant.
 4. The chain and sprocket assemblyof claim 1 wherein said first chain assembly is comprised of links eachhaving a pair of toes and a pair of inside flanks separated by a crotch,and each link defining a pair of apertures for receiving said pivotpins,some sets of links being comprised of links of a first inside flankconfiguration, and other sets of links being comprised of links of adifferent inside flank configuration.
 5. The chain and sprocket assemblyof claim 1 wherein said sprocket teeth are unevenly spaced.
 6. The chainand sprocket assembly of claim 1 wherein said first and second chainassemblies are separate and in a spaced-apart relation.
 7. The chain andsprocket assembly of claim 1 wherein said second chain assembly has somesets of links of a first configuration and other sets of links of adifferent configuration, said some sets of links being arranged in aprescribed pattern with said other sets of links.
 8. The chain andsprocket assembly of claim 1 wherein said first and second drivingsprockets are separate and in a spaced-apart relation, said first andsecond driven sprockets being separate and in a spaced-apart relation.9. The chain and sprocket assembly of claim 1 wherein at least one ofsaid first and second chain assemblies drivingly contacts a thirdsprocket.
 10. The chain and sprocket assembly of claim 1 wherein saidlinks of said first chain assembly contact the teeth of said firstdriving sprocket assembly with a first chordal action relationship, saidlinks of said second chain assembly contact the teeth of said seconddriving sprocket assembly with a second chordal action relationship,said first chordal action relationship being shifted in time withrespect to said second chordal action relationship.
 11. The chain andsprocket assembly of claim 1 wherein said pivot pins of said first chainassembly are offset with respect to said pivot pins of said second chainassembly.
 12. The chain and sprocket assembly of claim 1 wherein saidfirst and second chain assemblies are part of a single composite chainassembly.
 13. The chain and sprocket assembly of claim 1 wherein saidteeth of said first driving sprocket are offset from said teeth of saidsecond driving sprocket by approximately one-half pitch.
 14. The chainand sprocket assembly of claim 1 wherein said teeth of said firstdriving sprocket are offset from said teeth of said second drivingsprocket by approximately one-third pitch.
 15. The chain and sprocketassembly of claim 14 wherein said assembly includes a third chainassembly and third driving and driven sprockets, said teeth of saidthird driving sprocket being offset from said teeth of said seconddriving sprocket by approximately one-third pitch.
 16. A phased chainand sprocket assembly, comprising:first and second driving sprocketsconnected to a single drive shaft, said first and second drivingsprockets having a plurality of spaced teeth, said driving sprocketsbeing disposed in parallel relationship along said drive shaft, thelocation of the teeth of said first driving sprocket being offset withrespect to the teeth of said second driving sprocket, first and seconddriven sprockets connected to a single driven shaft, said first andsecond driven sprockets having a plurality of spaced teeth, said firstand second driven sprockets being disposed in parallel relationshipalong said driven shaft, the location of the teeth of said first drivensprocket being offset with respect to the teeth of said second drivensprocket, said drive shaft being operatively connected to a power inputand said driven shaft being operatively connected to a power output,said first driving sprocket being aligned with said first drivensprocket and having a first chain assembly drivingly connecting saidfirst driving sprocket with said first driven sprocket, said seconddriving sprocket being aligned with said second driven sprocket andhaving a second chain assembly drivingly connecting said second drivingsprocket with said second driven sprocket, said first and a second chainassemblies having a plurality of interleaved sets of inverted toothlinks, said links being adapted to contact the teeth of at least one ofsaid sprockets, pivot pins connecting adjacent sets of links, each linkdefining apertures for receiving said pivot pins, said first chainassembly having some sets of links of a first configuration and othersets of links of a different configuration, said some sets of linksbeing arranged in a prescribed pattern with said other sets of links,said first and second driving sprockets being part of a single compositedriving sprocket assembly, and said first and second driven sprocketsbeing part of a single composite driven sprocket assembly.
 17. A phasedchain and sprocket assembly, comprising:first and second drivingsprockets connected to a single drive shaft, said first and seconddriving sprockets being of substantially equal diameter and having aplurality of equally spaced teeth, said first and second drivingsprockets being axially aligned along said drive shaft, the location ofthe teeth of said first driving sprocket being circumferentially offsetwith respect to the location of the teeth of said second drivingsprocket, first and second driven sprockets connected to a single drivenshaft, said first and second driven sprockets being of substantiallyequal diameter and having a plurality of spaced teeth, said first andsecond driven sprockets being axially aligned along said driven shaft,the location of the teeth of said first driven sprocket teeth beingcircumferentially offset with respect to the teeth of said second drivensprocket, said first driving sprocket being aligned with said firstdriven sprocket and having a first chain assembly drivingly connectingsaid first driving sprocket with said first driven sprocket, said seconddriving sprocket being aligned with said second driven sprocket andhaving a second chain assembly drivingly connecting said second drivingsprocket with said second driven sprocket, said first and a second chainassemblies having a plurality of interleaved sets of inverted toothlinks, said links being adapted to contact the teeth of at least one ofsaid sprockets, pivot pins connecting adjacent sets of links, each linkdefining apertures for receiving said pivot pins, said first chainassembly having some sets of links that initially contact the sprocketwith flanks of a first configuration and other sets of links thatinitially contact the sprocket with flanks of a different configuration,said some sets of links being arranged in a prescribed pattern with saidother sets of links.
 18. The phased chain and sprocket assembly of claim17 wherein said first and second driving sprockets are part of a singlecomposite driving sprocket assembly, and said first and second drivensprockets are part of a single composite driven sprocket assembly. 19.The phased chain and sprocket assembly of claim 17 wherein said firstchain assembly is comprised of links each having a pair of toes and apair of inside flanks separated by a crotch, and each link defining apair of apertures for receiving said pivot pins,said some sets of linksbeing comprised of links having both inside flanks of a firstconfiguration, and said other sets of links being comprised of linkshaving both inside flanks of a different configuration.
 20. The phasedchain and sprocket assembly of claim 17 wherein said first and secondchain assemblies are separate and in a spaced-apart relation.
 21. Thephased chain and sprocket assembly of claim 17 wherein said initialcontacting flank is an inside flank.
 22. The phased chain and sprocketassembly of claim 17 wherein said teeth are circumferentially staggeredby an amount approximately equal to one-half the distance of thesprocket tooth pitch.
 23. The phased chain and sprocket assembly ofclaim 17 wherein said first chain assembly is comprised of links eachhaving a pair of toes and a pair of inside flanks separated by a crotch,and each link defining a pair of apertures for receiving said pivotpins,said some sets of links being comprised of links having an outsideflank of a first configuration, and said other sets of links beingcomprised of links having an outside flank of a different configuration.